Acoustical signaling apparatus



1, &,837

April 1 1924;

H. S. A. RYDBERG ACOUSTICAL SIGNALING APPARATUS Filed Nov. 22. 1923 Patented Apr. it,

UNETEM stars HELGE SVEN ALBERT RYDBERG, OF 130, SWEDEN.

ACQ'USTICAL SIGNALING MP Application filed November 22, 1923. Serial No. 676,454.

To all whom it may concern:

Be it known that I, HELGE SVEN ALBERT RYDBERG, a subject of the King of Sweden, residing at Ostra Forstadsgatan 21, Malmo, Sweden, have invented certain new and use ful Improvements in Acoustical Signaling Apparatus, of which the following is a specification,

This invention relates to that class of acoustical signaling apparatus in which the sound is produced by leading a gaseous or liquid pressure medium, by means of a supply pipe, against the centre of a diaphragm located against the outlet opening of the said supply pipe, thereby causing the said diaphragm to be forced aside and to vibrate, the pressure medium then escaping through the casing of the acoustical apparatus and a sound horn mounted thereon and communicatingtherewith.

ln acoustical apparatus of this kind the supply pipe for the pressure medium has been hitherto constructed in the term of a simple tube of such a diameter as the most favourable velocity 01 flow for the particular apparatus (determined by experiment) rendered necessary.

In the working of such acoustical signal-, ing apparatus it has been found that such a construction of the supply pipe for the ressure medium is injurious .to the eiticiency of the apparatus and also to the purity of the sound obtained. This is due to the fact that vibrations are set up in the supply pipe which cannot be well combined with the vibrations of the diaphragm and of the pressure medium in the exhaust chamber. Consequently a strong damping efiect is exerted on the development of these vibrations.

The object of this invention is therefore to overcome this disadvantage,thatis to say, to produce an apparatus of this kind in which this distiu'bing and damping effect is lessened or entirely removed.

According to this invention this object is attained by enlarging or increasing the internal diameter of the supply pipe adjacent that'end of the same which is contiguous to its outlet opening, which latter is located opposite the diaphragm, said enlargement or increase in diameter being greater than the, capacity required for the mere supply 0 pressure medium, and constructing the walls of the enlargement of the supply pipe to converge smoothly into the cross section ot the outlet opening of the said supply pipe lying against the diaphragm, thus avoiding all sudden changes of cross section and direction.

The invention is illustrated in the drawing in which the figure shows in section an acoustical signaling apparatus constructed according to the present invention.

Referring to the drawing, a flexible diaphragm 1 of metal or other suitable material is fixed, by means of a screwthreaded ring 2, so as to close one open end of a casing 3, into he opposite open end of which casing 3 is fixed one end of a sound horn 4:, the sound horn freely communicating with the interior of the casing 3.

The supply pipe 5, 6 for conveying the pressure medium comprises a tubular structure which passes through the wall of the casing 3. The external end of the supply pipe at 5 is connected, for instance by a flange as shown, with a pipe through which the pressure medium is supplied, while the supply pipe 6 within the casing is formed with an open end 7 of circular configuration, the edge of which open end lies against or close to the diaphragm 1. Therefore the pressure medium flows in the direction of the arrow X into the apparatus, and after the pressure medium, passing through the open end 7 of the supply pipe 6, has caused the diaphragm to vibrate, the pressure medium then passes through the casing 3 and through the sound horn 4 in the direction of the arrow Y. v.

To avoid the injurious effects before mentioned in this specification, the supply pipe 6 according to this invention is enlarge internally in diameter or widened, the enlarged portion being indicated as lying between the two'dottedlines C, Q, and in the example shown the supply pipe is constructed cylindrical, having the enlarged portion of a diameter indicated at D, although it is to be understood that the shape or form of the enlarged portion may be varied. An important point is however that the milargcment or widening indicated between the lines C, C terminates at such a distance from the diaphragm that there shall be a smooth transition between the enlarged portion and the open end 7 of the supply pipe (which opening, the diameter of which is indicated at (Z, is adjacent the diaphragm) to this end the structure maybe suitably curved between the enlarged portion of the supply pipe and the opening 7,

illltl) so as to provide a smooth transition of the pressure medium without any sudden change of direction and cross section. Hence the part of the supply pipe between its enlarged portion and its open end 7 is constituted by the uniformly contracted portion marked B.

The formation of the transition portion marked E between the external end of the supply pipe and the commencement of the enlargement thereof is not of primary importance because this part of the supply pipe is at a further distance away from the diaphragm and outside the range of the vibrations which set up disturbing influences.

The disturbing dampingof the supply chamber may also be removed to a great extent by giving the enlarged or widened portion. of, the supply pipe 6 such a volume that the individual vibration number of the chamber corresponds as closely as possible with the vibration number of the contents of the exhaust chamber of the apparatus (i. e. the casing and the horn).

Vfhat I claim as my invention and desire to secure by Letters Patent is 1. An acoustical signaling apparatus of the kind specified; comprising a diaphragm having its edge fixed to one open end of a. casing to close said end, a sound horn proceeding from the opposite open end of said casing, and a supply pipe for pressure medium passing to the interior of said casing and having its open end contiguous to said diaphragm of said casing, said supply pipe having an enlarged bore in the vicinity of said open end of said supply pipe adjacent said diaphragm, said enlarged bore of said supply pipe being greater than the capacity of the exhaust end of the supply pipe, said enlarged bore merging into the cross section of said exhaust opening ofsaid supply pipe next said diaphragm, smoothly and without any sudden changes of cross section and direction.

2. An acoustical signaling'apparatus of v the kind specified; comprising a diaphragm having its edge fixed to one open end oztla casingto close said end, a sound horn proceeding from the opposite end of said casing,

lineage? and a supply pipe for pressure medium passing through the wall of said casing to the interior thereof, and having its open end contiguous to said diaphragm of said casing, said supply pipe having an enlarged bore in thevicinity of said open exhaust end of said supply pipe adjacent said diaphragm, said enlarged bore of said supply pipe being greater than the said exhaust end of opening of said supply pipe next said diaphragm, smoothly and without any sudden,

changes of cross section and direction.

An acoustical signaling apparatus of the kind specified; comprising a casing of substantially conical formation, a diaphragm to close the larger open end of said casing, means for fixingthe edge of said diaphragm to the edge of said open end of said casing, a sound horn, means for fixing the smaller end of said sound horn to the smaller open end of said casing, a supply pipe for pressure medium formed with said casing, the delivery open end of said supply pipe being located contiguous to the interior surface of said diaphragm, and said supply pipe extending exteriorly of said casing, said supply pipe having an enlarged bore greater in dimensions than is necessary for the supply of the pressure medium, said enlarged bore being curved and gradually constricted to the opening of said supply pipe adjacent said diaphragm, so that said bore merges into the cross section of said opening of said supply pipe next said diaphragm, smoothly and without any sudden change of cross section and direction.

In witness whereof I-have hereunto set my hand in the presence oitwo witnesses.

' HELGHSVEN-ALBERT aromas.

, Witnesses:

THOMAS WILLIA Rooms, Lnsmn FRANK Rosales. 

